736 



THE WONDERS OF GEOLOGY. 



Lect. VII. 



{Lign. 168, jigs. 2, 6, 9, 10, 11,) there are two spiral 

 appendages (hence the name of the genus) which are closely 



... 2 



y: -J D 



LlGN. 1 



IliiWIi!!!!ll!!S"9 ff!? ' ?1 



Shells and Crinoidea from the Palaeozoic strata. 



Mountain limestone. Fig. 1. Leptsena punctata. 2. Spirifer trigonalis. 4. Cast 

 of Bellerophoncornu-arietis. 5. Euomphalus pcntangulatus. 7. Pentremites ellip- 

 ticus. 9. Spirifer trigonalis, showing one of the spiral processes in situ. 10. Spi- 

 rifer triangularis. 12. Orthoceratitc. 18. Septum of the same. 



Wenlock limestone. Fig. 3. Leptaena depresaa. 11. Spirifer octoplicatus. 



Oolite. Fig. 8. Terebratula allinis; tins figure was introduced by mistake. 



Recent shells. Fig. 6. Terebratula psittacea, showing the fringed spiral brachia, 

 and one of them extended; the perforated valve, and the lobe of the mantle being 

 removed. Fig. a b, a portion of the ciliary fringe magnified. 



coiled, and are often, like the substance of the shell itself, 

 changed into calcareous spar, (jigs. 2, 9) ; in specimens 



